The ball get's pretty mush and yes the band will break. I found that it shortened my strokes as the ball would rebound back fairly fast. It also changed the trajectory of my normal ball just so I could get it to bounce back within a certain sweet spot. I saw this being used at a flea market where the guy promoting it was hitting very well. I'm sure that with some practice and knowing where you want to place the anchor weight in regards to your position you could find it useful.

I prob wouldn't buy one if I where to do it all over again. I don't use it at the court (except a few times when first purchased). I did use it in the driveway though. If I need to warm up at the court I just do jumping jacks, run in place, and swing the racquet. If I have a court to myself I'll get close to the next and hit ground strokes into the net or just use the ball hopper/basket to hit fr the base line.

Those have been around at least 20-30 years. I had one as a kid. Yeah it doesn't take much to break the rubber band so best for beginners/children developing hand eye coordination and not so great for adults or anyone who can really hit the ball (you'll either snap the band or hit hard enough to move the base). Also doesn't work as well if you put any spin on the ball.